This application relates to magnetic disc drives and more particularly to apparatus for reducing xe2x80x9chead-slapxe2x80x9d when a disc drive undergoes a large shock.
A computer disc drive includes one or more discs mounted for rotation about a spindle axis. The discs are typically coated with a magnetic medium for storage of digital information in a plurality of circular, concentric data tracks. A spindle motor rotates the discs about the axis to allow a head or xe2x80x9csliderxe2x80x9d carrying electromagnetic transducers to pass over each disc surface and read information from or write information to the data tracks.
The slider is typically formed from a ceramic block having a specially etched surface that forms an air xe2x80x9cbearingxe2x80x9d as the disc rotates beneath the slider. The lifting force provided by the air bearing surface causes the slider to lift off and xe2x80x9cflyxe2x80x9d a very small distance above the surface of the disc as the disc spins up to its operating speed. Although the fly height of the slider is only a fraction of a micron, this thin film of air between the slider and the disc prevents damage to the fragile magnetic coating on the surface of the disc.
The slider is preferably moved between data tracks across the surface of the disc by an actuator mechanism such as a rotary voice coil motor. The actuator includes arms attached to each of the sliders by flexible suspensions. Each suspension essentially comprises a flat sheet metal spring that exerts a controlled preload force on the slider in the vertical direction (i.e., against the surface of the disc). The preload force supplied by the suspension effectively counters the lift force generated by the slider and prevents the slider from flying too far off the surface of the disc. Although relatively flexible in the vertical direction, the suspension is relatively stiff in the lateral direction in order to provide for precise lateral positioning of the slider over the closely spaced data tracks.
Although the downward preload force supplied by the suspension is effectively countered by the lifting force generated by the slider during rotation of the disc, that same preload force typically forces the slider to rest on the surface of the disc once the disc stops spinning and the lifting force dissipates (e.g., when the disc drive is powered down). During these periods of inactivity, and particularly during assembly, shipping and handling of the disc drive before the drive is assembled within a computer, the fragile magnetic coating on the surface of the disc is susceptible to damage from accidental vertical displacement of the slider, such as by a shock event.
Vertical displacement of the slider may occur when the disc drive is subjected to a shock of sufficient magnitude to cause the suspension and the attached slider to move away from the disc surface (either on the initial shock or on a rebound from the initial shock). Although the preload force supplied by the suspension tends to hold the slider against the disc during small shocks, a sufficiently large shock (e.g., a shock 200 times the acceleration of gravity or 200 xe2x80x9cGsxe2x80x9d) will typically overcome the preload force and cause the slider to be pulled off the disc surface. The return impact of the slider against the disc surface can cause severe damage to the thin magnetic coating on the surface of the disc. If the shock event occurs during operation of the disc drive, the damage to the disc coating may create an unusable portion or sector of the disc and a potential loss of data stored on that portion of the disc. However, most large shock events typically occur during periods of inactivity, as described above, when the slider is positioned along an inner radial portion or xe2x80x9cpark zonexe2x80x9d of the disc not used for data storage. Regardless of whether the impact occurs in the data region or the park zone of the disc, the impact typically generates debris particles that can migrate across the surface of the disc and interfere with the air bearing surface of the slider, thereby causing damage to more vital regions of the disc during disc operation and possibly leading to a disc xe2x80x9ccrash.xe2x80x9d
Previous efforts to minimize the above described xe2x80x9chead-slapxe2x80x9d phenomenon have focused on either increasing the preload force applied by the suspension or reducing the mass of the suspension to reduce the lift-off force. That is, the lift-off force equals the acceleration of the shock event (the xe2x80x9cG-forcexe2x80x9d) multiplied by the combined mass of the suspension and the slider. Therefore, a reduction in the mass of the suspension leads to a reduction in the force applied to the slider during a shock event and thus to improved shock performance for the disc drive. As an alternative to reducing the mass of the suspension, some prior art suspension designs incorporate a counterweight at a proximal end of the suspension to help balance the overall mass of the suspension. Once such design is shown in U.S. Pat. No. 5,936,803 entitled xe2x80x9cDisc Drive Having a Mass Balanced Head Gimbal Assembly.xe2x80x9d A further alternative solution to the head-slap problem is to fix motion limiters or cushions atop the suspension to both limit the vertical displacement of the suspension and to damp the impact of the suspension.
Unfortunately, the prior art solutions of altering the design of the suspension (such as by reducing the mass of the suspension or by adding additional mass in the form of a counterweight) and of adding cushions/motion limiters to the suspension in order to improve the shock resistance of the suspension can be detrimental to the primary function of the suspension. Specifically, the most important function of the suspension is to accurately position the slider over the densely spaced data tracks. Toward this end, disc drive suspensions are optimized to move in both a lateral direction but also to provide resiliency in the vertical direction to allow the slider to follow small oscillations in the surface of the disc as the disc rotates about the spindle axis. However, when the design of these optimized suspensions is altered as described above to combat the head-slap phenomenon, the result is typically a reduction in the xe2x80x9cnormalxe2x80x9d operating performance of the suspension. That is, when the suspension is called upon to perform additional tasks such as reducing head-slap, it is likely that the new task will interfere with the primary task (e.g., track following) performed by the suspension. This trade-off in performance of the suspension is particularly inefficient since the xe2x80x9cnew taskxe2x80x9d (high G-force shock protection) occurs only rarely, if at all, during the life of the disc drive.
Accordingly, there is a need to reduce the damage caused by the xe2x80x9chead-slapxe2x80x9d phenomenon while not interfering with the basic design of the disc drive suspension. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.
The present relates to a disc drive that includes a pivotal elongated member attached to an end of an actuator arm for contacting a suspension of the disc drive only during a shock event, thereby preventing or substantially reducing damage to the disc resulting from a head-slap.
In accordance with one embodiment of the present invention, a disc drive assembly has an actuator for moving an actuator arm above the surface of a rotating disc. A suspension connects a slider to the actuator arm to maintain the slider substantially engaged with the disc surface in the absence of a shock event. A head-slap arrestor attached to the actuator arm includes a finger extending over the suspension, wherein a distal end of the finger pivots between a first position at a predetermined height above the suspension, in the absence of a shock event, and a second position engaging the suspension during a shock event to maintain the slider substantially engaged with the disc surface. The head-slap arrestor may be implemented as a paddle pivotally attached to the actuator arm and secured to a proximal end of the finger along a hinge axis to allow for pivoting motion of the paddle and the finger about the hinge axis.
The present invention can also be implemented as a head-slap arrestor for a disc drive wherein the disc drive includes an actuator arm that moves above the surface of a spinning disc, and wherein a slider is connected to the actuator arm by a suspension to maintain the slider substantially engaged with the disc surface in the absence of a shock event. The head-slap arrestor includes attachment feet adapted to be secured to the actuator arm and a paddle secured to the attachment feet along a hinge axis so that the paddle is suspended above the attachment feet. A finger includes a proximal end attached to the paddle along the hinge axis and a distal end extending away from the paddle so that the paddle and the finger pivot in opposite directions about the hinge axis. The distal end of the finger is adapted to extend a predetermined height above the suspension in the absence of a shock event, and is further adapted to pivot about the hinge axis and engage the suspension to maintain the slider substantially engaged with the disc surface during a shock event.
Yet another embodiment of the present invention may be described as a disc drive assembly having a suspension maintaining a slider substantially engaged with a surface of a disc in the absence of a shock event. The invention includes a means for applying a force to the suspension to maintain the slider substantially engaged with the disc surface when the disc drive assembly undergoes a shock event. The means for applying a force to the suspension includes means for scaling the force to match a force of the shock event. The means may further include an elongated member pivotally attached to an actuator arm of the disc drive wherein the elongated member does not engage the suspension in the absence of a shock event.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.